I'm not taking away from Andrew Jackson one bit when I say that Harriet Tubman kicked ass. If we're going to open up currency from just Presidents or Founding Fathers, Tubman would be a great choice.
It is not correct to call this "Political Correctness" - reading her biography as a child was a revelation to just what heroes did in the face of injustice and butchery. (See what fate black Union soldiers met if you dispute the latter.)
Now, look at some of the posts here. Just a few up from yours is one that refers to Harriet Tubman as a "thing". That's revolting. Part of celebrating the possibility of her getting on the currency is that it's a chance to figuratively kick these racist bastards in the balls.
And yes, the comment about Tubman was reprehensible, but you know and I know that if she appears on the $20, a lot of people aren't going to use them anymore. Part of the reason is no one knows who she is thank to liberals destroying education, and part is Harriet isn't exactly telegenic.